In the prior art there are described imidazolidinone derivatives having an aryl group on one nitrogen atom and an amino-lower alkyl group on the other nitrogen atom; South African Patent No. 62/4312. Other imidazolidinone derivatives where the aminic group is represented by a radical ##STR2## besides being lower alkyl, can also represent, taken together with the nitrogen atom, a heterocyclic 5- to 7-membered ring, are also known; ibid.
W. B. Wright et al., J. Med. Chem. 9, 852, 1966, report the results of pharmacological tests on a series of compounds of the class covered by the above-mentioned South African Patent and point out that 1-(m-chlorophenyl)-3-(2-dimethylaminoethyl)-2-imidazolidinone (imidoline) is the most promising one from the biological point of view.
It has now surprisingly been found that the introduction of an azetidine ring leads to imidazolidinone derivatives much more active than those described in the literature.